BlueGreenDeployment - http://martinfowler.com/bliki...
"One of the challenges with automating deployment is the cut-over itself, taking software from the final stage of testing to live production. You usually need to do this quickly in order to minimize downtime. The blue-green deployment approach does this by ensuring you have two production environments, as identical as possible. At any time one them, let's say blue for the example, is live. As you prepare a new release of your software you do your final stage of testing in green environment. Once the software is working in the green environment, you switch the router so that all incoming requests go to the green environment - the blue one is now idle." - Fred Yankowski